rotted sole plate replacement

i have an old single story wood frame garage that has recently been re-sided.the rotten sole plates on the endwalls are a single layer of 2x8 on cinderblock -it appears the floor slab was poured after the garage was framed and its height exceeds the plate height-.i was wondering after supporting the existing wall with a cripple wall ,can i cut up on the wall studs an inch and 1/2 or three inches if necessary to provide me with the space i need to remove the old plates and install the new one?

Sill insulation will air seal the concrete to plate connection as well as act as a capillary break to prevent water wicking into the wood. It comes in a roll. About 6" wide 1/4" thick and is pink foam material.